Butterfly valve seat

ABSTRACT

In a butterfly valve of the type wherein an annular flexible seat ring circumscribing the fluid flow channel cooperates with an inclined circumferential sealing surface on a rotatably mounted butterfly disc to open and close the flow channel, an improvement is made to permit the valve to resist internal fluid pressure with equal effectiveness regardless of the direction from which applied. The disc deflects in the downstream direction to the same extend upon the application of a given fluid pressure (up to the design pressure of the valve) regardless of the direction from which the pressure is applied; whereas the annular flexible seal tends to deflect to a greater extent than this when the pressure is applied from the direction of convergence of the inclined circumferential sealing surface and to a lesser extent than this when the internal fluid pressure is applied from the opposite direction.

Unite States atent (72] Inventors David A. llelman Berlin; Michael E.Miles, Northborough; James F. Donnelly, Worcester, all of Mass. 1211Appl. No 732,729 [22] Filed May 28, 19611 [45] Patented Sept. 28, 1971I73] Assignce .lamcsbury Corporation Worcester, Mass.

[54] BUTTERFLY VALVE SEAT 9 Claims, 3 Drawing Figs.

[52] U.S.Cl 251/173, 251/306, 251/317 {51] lnt.Cl F16k 5/16 [50] Fieldof Search 251/173, 175, 305, 317, 306

[56] References Cited UNITED STATES PATENTS 2,893,682 7/1959 Hintzman251/173 3,307,633 3/1967 Newall Primary Examiner-Harold W. WeakleyAttorneys-Robert F. Conrad and Kurt Shaft'ert ABSTRACT: In a butterflyvalve olthe type wherein an annular flexible seat ring circumscribingthe fluid flow channel cooperates with an inclined circumferentialsealing surface on a rotatably mounted butterfly disc to open and closethe flow channel, an improvement is made to permit the valve to resistinternal fluid pressure with equal effectiveness regardless of thedirection from which applied. The disc deflects in the downstreamdirection to the same extend upon the application of a given fluidpressure (up to the design pressure of the valve) regardless of thedirection from which the pressure is applied; whereas the annularflexible seal tends to deflect to a greater extent than this when thepressure is applied from the direction of convergence of the inclinedcircumferential sealing surface and to a lesser extent than this whenthe internal fluid pressure is applied from the opposite direction.

BUTTERFLY VALVE SEAT BACKGROUND OF THE INVENTION This invention relatesto rotary fluid control valves of the butterfly type wherein a disc ismounted for rotation between the open position, in which the disc liessubstantially parallel to the axis of the fluid flow channel through thevalve, and the closed position in which the disc lies perpendicularly tothis axis. The disc cooperates with an annular flexible seatcircumscribing the fluid flow channel to shut off fluid flow through thechannel. More particularly, the invention relates to such valves inwhich the action of the internal fluid pressure acting upon the valveserves to improve the cooperation between the flexible seat and thedisc, that is wherein increased fluid pressure actually tends to reducethe likelihood of fluid leakage past the valve.

Although butterfly valves of the general configuration of thosedisclosed by White in U.S. Pat. No. 2,980,388 and Swain in US. Pat. No.3,282,558 have found acceptance for certain types of service, thesevalves are nevertheless considered limited-service valves because of anumber of disadvantages from which they inherently suffer.

Hintzman et al. in US. Pat. No. 2,893,682 disclose a valve constructionwherein the circumferential sealing surface and the flexible seat arecontoured to complement each other and make mere sliding contact in theabsence of internal fluid pressure. The application of such fluidpressure from the direction of convergence of the sealing surface on thebutterfly disc forces the flexible seat into more intimate contact withthe sealing surface on the disc so as to reduce leakage. When the fluidpressure is applied from the opposite direction to this valve, however,the flexible seat tends to be lifted away from the circumferentialsealing surface permitting fluid to leak past the valve. The patenteespoint out that this feature is actually useful when the valve isemployed in one special type of service, i.e. to control the flow of ahighly volatile fluid which tends to build up gas pressure as it iswarmed. In general, however, it is more desirable, and for many types ofservice absolutely necessary, to provide a valve which will resist fluidpressure regardless of the direction from which it is applied.

It is an object of this invention to provide an improved butterfly valvecapable of service in a system wherein internal fluid pressure may beapplied from either direction to the valve.

It is a further object of this invention to provide an improvedbutterfly valve in which fluid pressure acts upon the valve to improvethe sealing effectiveness thereof, regardless of the direction fromwhich the fluid pressure is applied.

Yet another object of this invention is to provide an improved butterflyvalve in which sealing occurs by virtue of deflection, includingcompression and flexing, of the seat and in which this sealing action isfortified by the action of internal fluid pressure upon the valve,regardless of the direction from which this fluid pressure is applied.

Still another object of this invention is to provide a flexible set forrotary fluid valves which will be compressed to form a tighter seal bythe action of fluid pressure, regardless of the direction from whichthis pressure is applied.

These and other objects and advantages of the invention, and the mannerof their attainment, will become apparent to those skilled in this artfrom a consideration of this specification when taken in conjunctionwith the appended drawings.

SUMMARY OF THE INVENTION The improvement of this invention isparticularly applicable to butterfly valves wherein a butterfly discelement is mounted for rotation about an axis perpendicular to the axisof the fluid flow channel defined by the valve housing, and wherein anannular flexible seat circumscribing the fluid flow channel isjuxtaposed to cooperate with a sealing surface circumscribing the disc.This circumscribing sealing surface is preferably inclined, i.e. it is asegment of a converging surface, convergence occurring at a point on theextension of the fluid flow axis. For instance, the circumscribingsealing surface may be a frustum of a cone or a segment of a sphere or aspheroid. The rotatable mounting of the disc may be: a shaft whichextends through a packing gland in the valve body to an external valvehandle.

The application of internal fluid pressure to either face of the valvedisc when the valve is closed inherently causes some deflection of thedisc in the direction away from the pressure source. This deflectionwill be the sum total of the deflections caused by shaft bending,clearance between the shaft and its bearings, compression of thebearings by the shaft, and displacement of the disc relative to theshaft if these two elements are not attached to each other with absoluterigidity. The magnitude of this deflection of the disc will generally beindependent of the direction of application of the fluid pressure, andis a function of the magnitude of the resultant internal fluid pressureapplied to it (up to the design pressure of the valve).

One way to accomplish such isotropic deflection of the disc, i.e.deflection in response to internal flruid pressure regardless of thedirection from which it is applied, is to provide a butterfly element ofunitary construction having a disc element and a gudgeon element, theshaft passing through a bore of a gudgeon and being internally connectedthereto for mutual rotation.

The other requirement for the achievement of the objectives of thisinvention is to provide an annular flexible seat which tends to bedeflected anisotropically by internal fluid pressure, i.e. which tendsto be deflected to a greater extent by the application of internal fluidpressure (up to the design pressure of the valve) when that pressure isbeing applied from the direction in which the circumscribing sealingsurface converges and to a lesser extent when the internal fluidpressure is being applied from the opposite direction. The tendency ofthis seat to deflect in response to fluid pressure emanating from thedirection of convergence is desirably greater than the tendency of thedisc to deflect, but the tendency of the seat to deflect in response tofluid pressure when it emanates from the opposite direction is desirablyless than the tendency of the disc to deflect.

It will be seen that application of flluid pressure from the directionof convergence will cause the inevitable downstream displacement of thevalve disc. But, when the above-stated criteria are met, thisapplication of internal fluid pressure will cause the flexible seat totend to be displaced downstream by an even greater amount, forcing thelatter into even tighter relationship with the circumscribing sealingsurface and improving the sealing effectiveness of the valve as comparedto before the application of this fluid pressure. On the other hand,when internal fluid pressure is applied to the valve from the oppositedirection, the disc will be displaced toward the direction ofconvergence by a certain magnitude by the flexible seat will tend to bedisplaced in that direction to only lesser extent, thereby againincreasing the sealing effectiveness of the valve as internal fluidpressure increases.

It is desirable that the flexible annular seat be positioned in relationto the sealing surface of the disc so that even in the absence ofinternal fluid pressure the seat tends to be deflected by the sealingsurface when the disc is in the closed position, i.e. that seat iscompressed by virtue of being an interfering location with respect tothe sealing surface of the disc. The action of these cooperating partsin response to the application of internal fluid pressure, describedabove, then serves to reinforce the initial sealing action, therebyproviding a butterfly valve which seals positively and effectivelyagainst fluid leakage in all ranges of internal fluid pressure andregardless of the direction of application of this pressure.

A number of ways of achieving the required directionally selectivedeflection property in the flexible seat means will be disclosed hereinalthough it will be understood that other ways of achieving suchdirectional selectivity or anisotropicity are applicable to thisinvention.

The flexible annular seat may conveniently be a ring of elongated crosssection having an annular outer portion adapted to be dripped andrestrained by rigid elements of the valve disposed on either side of itand immediately adjacent thereto. The inner portion of this flexibleseat, i.e. the portion adjacent to the annular opening thereof, isunrestrained and free to be deflected by contact with the sealingsurface of the disc, or by the action of internal fluid pressure, orboth. The portion of the seat connecting this inner portion with theouter portion may be thought of as a linking portion.

In one embodiment of the invention the rigid gripping element of thevalve disposed on the same side of the flexible seat as the direction ofconvergence contacts the annular seat from the radial outside extremitythereof toward the center thereof over a greater proportion of theradius of the seat than does the corresponding rigid element on theother side of the flexible seat. As a result, deflection of the radiallyinner portion of the seat in response to fluid pressure from thedirection of convergence will occur by flexing about a fulcrum (theradially annular inner terminus of the rigid element) further from thecenter of the annular seat (i.e. the flow axis) than is the fulcrum forflexing in the opposite direction. Reflection about either fulcrumdistorts the flexible seat into a configuration with a given radius ofcurvature. A configuration with a relatively small radius of curvatureis more highly distorted than one with a relatively large radius ofcurvature. The more remote from the center of the annular seat (i.e. theflow axis) that the fulcrum for flexing the flexible seat is located,the more readily the seat can deflect and the greater will be the radiusof the curvature of the configuration which is imparted to the seat.Therefore, the seat will tend to deflect more readily away from thedirection of convergence than toward it.

In another embodiment, a rigid compression surface is juxtaposedadjacent to the inner portion of the seat and on the same side thereofas the direction of convergence. The loca tion of this compressionsurface is such that incipient deflection of the seat in the directionof convergence (such as would be induced by internal fluid pressureemanating from the opposite direction) will bring the annularly innerportion of the seat into contact with it. Further deflection of the seatin the same direction compresses the seat against this compressionsurface, so that it has only a slight tendency to deflect in thisdirection. On the other hand, there being no compression elementcorrespondingly located on the other side of the seat, the ability ofthe seat to tend to deflect in that direction is not so limited.

In a third embodiment of the invention the anisotropic tendency of theseat to deflect is accomplished by exposing different amounts of area onthe respective faces of the flexible seat to the resultant force createdby internal fluid pressure. Inasmuch as this resultant force whichcauses the deflection in the flexible seat referred to is force in thedirection of the flow axis, the significant area for this purpose is theprojection of the actual area of the seat exposed to this pressureprojected upon a plane normal to the flow axis to the valve. If theprojection of this area upon such a plane on the side of the valve inthe direction of convergence is sufficiently greater than that on theother side, the desired directionally differential effect is obtained.

Combinations of these effects, or other means either singly or incombination with each other or with the means here described may beemployed to achieve the requisite anisotropic tendency of the seat todeflect. Thus, for instance, the seat may be constructed to be ofgraduated stiffness from one surface to the other thereof. Suchgraduation may be accomplished by a gradation ,of material properties.The seat may be constructed of any materialhaving the requisiteflexibility properties, i.e. a stiffly flexible material.Fluorine-containing polymers such as tetrafluoroethylene are highlysuitable. In some instances, metals with sufficient springiness may bepreferred. Unlike many butterfly valve designs of the prior art, thevalves incorporating the improvements of the instant invention do notrequire that the seat material be elastomeric, such as seats made ofnatural or synthetic rubber.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an elevation, partially incross section, of a butterfly valve of the improved type disclosed inthis application.

FIG. 2 is a cross-sectional representation of a portion of an annularflexible seal which may be employed in the improved valve of the instantinvention.

FIG. 3 is an enlarged cross-sectional representation of the zone ofcooperation between the annular seat and the sealing surface on the discof the improved valve of the instant invention shown in FIG. 1.

DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INSTANT INVENTION Depictedin FIG. 1 is a valve 10 shown optionally equipped with motorized valveoperator Ila, the details of which are not relevant to this invention.Valve 10 is comprised of valve housing 11 defining flow channel 12 ofcircular cross section therethrough, butterfly disc 13 mounted forrotation with shaft 14, annular flexible seat I5 and seat retainer ring16.

The fluid flow channel 12 has an imaginary flow axis indicated at 13a.Shaft 14 is essentially perpendicular to flow axis 13a. The shaft 14 ismounted for rotation in valve housing 11 with the aid of lower bearingmeans 17 and upper bearing means 18, neither of which is shown indetail. Plug 19 is inserted in the bottom of the shaft bore to preventthe escape of internal fluid pressure. Stuffer box means 19a, also notshown in detail, permit the emergence of shaft 14 from the upper end ofvalve housing 11 without the loss of internal fluid pressure.

Butterfly disc 13 is surrounded by circumferential sealing surface 20.This sealing surface is inclined with respect to flow axis 13a. Anotherway of describing sealing surface 20 is by pointing out that it is asegment of a larger geometric (i.e. imaginary rather than concretelypresent) surface which converges at a point located substantially alongthe extension of flow axis 13a. As viewed in FIG. 1, circumferentialsealing surface 20 of disc 13 converges toward the right, and this willbe referred to as the direction of convergence.

FIG. 3 shows, in enlargement, that portion of the valve in which thecooperation between sealing surface 20 of disc 13 and flexible annularseat 15 must occur. It will be recognized that in FIG. 3 the directionof convergence is upward, i.e. toward the top of the drawing.

The flexible annular seat 15 has an annularly outer portion 21, and anannularly inner portion 22 which are joined by linking portion 23. Itwill be seen that outer portion 21 has parallel surfaces 24 and 25adapted to be gripped and restrained by adjacent rigid elements 26 and27 respectively. As may be seen from FIG. 1, rigid element 26 is asurface of seat retainer ring 16 and rigid element 27 is a surface ofvalve housing 11.

Inner portion 22 of annular flexible seat 15 is shown in FIG. 3 in itstotally undeflected position, i.e. in the position which it would occupyif disc 13 were rotated out of contact into the open position. It willbe understood from the overlap 28, shown in FIG. 3 in dark shading toexist between annular seat 15 and disc 13, that a force fit existsbetween these elements. That is, when disc 13 is rotated into the closedposition, an incipient deflection of seat 15 occurs, assuring positivesealing of the valve even in the absence of internal fluid pressure.

Deflection on inner portion 22 of valve seat 15 occurs mainly by virtueof flexure at linking portion 23 of the seat. To accommodate thisflexure, linking portion 23 is deeply relieved at 29.

Upon application of internal fluid pressure from the direction ofconvergence, i.e. from the right in FIG. I or from the top of FIG. 3,disc 13 is displaced in a downstream direction (i.e. to the left in FIG.1 or downward in FIG. 3) by a magnitude which is a function of themagnitude of the internal fluid pressure. Those skilled in this art willreadily understand that this function can be influenced by suitableselection of the compressibility and other properties of bearings 17 and18, design of the proper clearance between shaft 14 and bearings 17 and18, the rigidity of shaft 14 and by suitable design of the connectingmeans between disc 13 and shaft 14.

This same application of fluid pressure will cause annular flexible seat15, and more specifically inner portion 22 thereof, to tend to deflectin a downstream direction in a magnitude greater than the deflection ofdisc 13. In so doing, inner portion 22 of seat will be compressed withgreater force than theretofore against circumferential sealing surface20, thereby reinforcing the sealing effect which existed by virtue ofthe interference fit between these two elements before the applicationof internal fluid pressure.

If, alternatively, the fluid pressure applied to the valve emanates fromthe direction opposite to the direction of convergence (i.e. from theleft in FIG. 1 or from the bottom in FIG. 3) disc 13 will again bedisplaced in a downstream direction (not to the right in FIG. l and tothe top in FIG. 3) by a magnitude related to the magnitude of theinternal fluid pressure. Inner portion 22 of annular seat 15, however,tends to be deflected in the downstream direction by a lesser magnitudethan the displacement of disc 13. This again causes an increase in thedegree compression of seat 15 by annular sealing surface as the internalfluid pressure is increased.

The reason why inner portion 22 of annular seat 15 tends to be deflectedmore in response to the application of internal fluid pressure when thatapplication is from the direction of convergence than when it is fromthe opposite direction may be understood by a consideration of FIG. 3.It will be seen that deflection of inner portion 22 in response to fluidpressure emanating from the direction of convergence (i.e. from the top)is accomplished by the downward flexure of linking portion 23 using thepoint b on ring embossment 30a on rigid element 27 as a fulcrum. On theother hand, if fluid pressure is applied from the opposite direction,deflection of inner portion 22 would have to occur by virtue of flexureof linking portion 23 about point 31 on rigid surface 26 on seatretainer ring 16 as a fulcrum. Fulcrum 30b is, of course, measurablyfurther from the center of annular seat 15 (and of disc 13) than isfulcrum 31, so that deflection in an upward direction must occur byvirtue of flexure to a configuration of a measurably smaller radius ofcurvature than when the internal fluid pressure is applied from the top.

Although it is the cooperation between seating surface 34% of the innerportion 22 of seat 15 with circumferential sealing surface 20 of thedisc which provides the sealing action of the valve, the relationshipbetween surface 32 on the back of inner portion 22 and rigid surface 33on rigid element 26 also plays an important role in the functioning ofthe improved valves of this invention. As has already been stated, innerportion 22 is shown in FIG. 3 in the position it would occupy when disc13 is in the open position. When disc 13 is closed, inner portion 22 isdeflected slightly so that surface 32 thereof comes closer to surface 33without touching it. However, further upward deflection of inner portion22, such as would be caused by the application of internal fluidpressure emanating from the direction opposite to the direction ofconvergence (i.e. from the bottom) would cause surfaces 32 and 33 tocome into still closer proximity until they finally contact each other,whereafter any further application of internal fluid pressure from thesame direction would cause compression of inner element 22 of annularseat 15. The distance by which surfaces 32 and 33 are spaced apart mustbe sufficient to permit not only the displacement of inner portion 22accompanying the closing of disc 13 described above, but also thethermal expansion of the components which may be encountered within thetemperature service range for which the valve is designed.

Yet another factor which contributes to the anisotropic tendency ofannular seat 15 to deflect, depending upon the direction of applicationof internal fluid pressure, is the effective area upon which that fluidpressure acts. When the internal fluid pressure is applied from thedirection of convergence (Le. from the top), this fluid pressure actsupon seat 15 from the point of contact thereof with disc 13 back pastfulcrum 31. When the fluid pressure emanates from the oppositedirection, the area upon which it acts runs from the lowest point ofcontact between seat 15 and disc 13 somewhat beyond point 30. Internalfluid pressure acting on a given segment of seat area can have one oftwo types of effect. If the given segment of seat area is supported,i.e. if the surface opposite thereto abuts a rigid surface, it willmerely be compressed. On the other hand, segments of seat which areunsupported will be flexed in a downstream direction by a resultantforce which is the product of the magnitude of the pressure times theprojection of the area of the unsupported segment of the seat on a planeperpendicular to the flow axis (in FIG. 3, any horizontal plane). Ifthis product is greater for pressure applied from the direction ofconvergence (i.e. from the top) than in the opposite direction, thedesired anisotropicity of the annular flexi' ble seat will result.

We claim: 1. In a butterfly valve comprising annular flexible seat meanscircumscribing the fluid flow channel defined by the interior surfacesof a valve housing, a disc mounted in said valve housing for rotationabout an axis substantially perpendicular to the flow axis of said fluidflow channel, and a circumferential sealing surface on said disccooperating with said seat means to block the flow of fluid through saidfluid flow channel when said disc is rotated into the closed position,said sealing surface being a segment of a substantially convergingsurface, the improvement comprising:

providing annular flexible seat means which tend to deflect more thanthe said disc in the downstream direction when internal fluid pressureof a given magnitude is applied from the direction of convergence ofsaid sealing surface and which also tend to deflect less than said discwhen said fluid pressure is applied from the opposite direction,

whereby internal fluid pressure, regardless of the direction from whichit is applied, increases the sealing effectiveness of said seat means onsaid disc. 2. The improvement of claim 1 wherein said annular flexibleseat means comprise an annular outer element adapted to be constrainedbetween adjacent surfaces of the elements constituting said valve, aninner element disposed within said annulus of said outer element andcontaining an inclined seating surface adapted to seat against saidconvergent circumferential sealing surface on said disc, and a flexiblelinking element joining said inner element to said outer element andpermitting said inner element to deflect in a downstream direction inresponse to the application thereto of fluid pressure emanating fromeither direction along said fluid flow channel.

3. In a butterfly valve comprising annular flexible seat meanscircumscribing the fluid flow channel defined by the interior surfacesof a valve housing, a disc mounted in said valve housing for rotationabout an axis substantially perpendicular to the flow axis of said fluidflow channel, an a circumferential sealing surface on said disccooperating with said seat means to block the flow of fluid through saidfluid flow channel when said disc is rotated into the closed position,said sealing surface being a segment of a substantially convergingsurface, the improvement comprising:

providing annular flexible seat means which tend to deflect more thanthe said disc in the downstream direction when internal fluid pressureof a given magnitude is applied from the direction of convergence ofsaid sealing surface and which also tend to deflect less than said discwhen said fluid pressure is applied from the opposite direction,

whereby internal fluid pressure, regardless of the direction from whichit is applied, increases the sealing effectiveness of said seat means onsaid disc,

and wherein said annular flexible seat means comprise an annular outerelement adapted to be constrained between adjacent surfaces of theelements constituting said valve, an inner element disposed within saidannulus of said outer element and containing an inclined seating surfaceadapted to seat against said convergent circumferential sealing surfaceon said disc, and a flexible linking element joining said inner elementto said outer element and permitting said inner element to deflect in adownstream direction in response to the application thereto of fluidpressure emanating from either direction along said fluid flow channel,and

wherein the deflection of said inner element occurs by virtue of flexurein said linking element about one of a pair of pivot points on saidadjacent surface, said pivot point on that side of said annular seatmeans facing said direction of convergence being located closer to thecenter of said annular seating means than said pivot point on the otherside thereof, whereby internal fluid pressure of a given magnitude tendsto deflect said inner element more when applied from the said directionof convergence than when applied from the opposite direction. 4. Theimprovement of claim 2 wherein a rigid element adjacent to said innerelement intercepts said inner element as it tends to deflect in responseto internal fluid pressure of a magnitude not greater than the designpressure of said valve and emanating from the direction opposite to saiddirection of convergence.

5. The improvement of claim 1 wherein a rigid element is locatedadjacent said flexible annular seat means and on the same side thereofas the said direction of convergence, said rigid element beingpositioned sufficiently close to said flexible annular seat means tointercept the deflection of said annular flexible seat means in responseto internal fluid pressure of a magnitude not greater than the designpressure of said valve and emanating from the direction opposite to saiddirection of convergence.

6. in a butterfly valve comprising annular flexible seat meanscircumscribing the fluid flow channel defined by the interior surfacesof a valve housa disc mounted in said valve housing for rotation aboutan axis substantially perpendicular to the flow axis of said fluid flowchannel, and a circumferential sealing surface on said disc cooperatingwith said seat means to block the flow of fluid through said fluid flowchannel when said disc is rotated into the closed position, said sealingsurface being a segment of a substantially converging surface, theimprovement comprising:

providing annular flexible seat means which tend to deflect more, thanthe said disc in the downstream direction when internal fluid pressureof a given magnitude is applied from the direction of convergence ofsaid sealing surface and which also tend to deflect less than said discwhen said fluid pressure is applied from the opposite direction,

whereby internal fluid pressure, regardless of the direction from whichit is applied, increases the sealing effectiveness of said seat means onsaid disc wherein a rigid element is located adjacent said flexibleannular seat means and on the same side thereof as the said direction ofconvergence, said rigid element being positioned sufficiently close tosaid flexible annular seat means to intercept the deflection of saidannular flexible seat means in response to internal fluid pressure of amagnitude not greater than the design pressure of said valve andemanating from the direction opposite to said direction of convergence,and

wherein said rigid element is located in such proximity to said flexibleannular seat means as to permit less deflection thereof in saiddirection of convergence than said flexible annular seat means Is freeto deflect in the opposite direction. 7. The improvement of claim 1wherein the projection upon a plane perpendicular to the said flow axisof that portion of the surface of said flexible seat means which is freeto flex and is exposed to internal fluid pressure when said pressure isemanating from the direction of convergence contains a greater area thanthe projection upon the same plane of that portion of the surface ofsaid flexible seat means which is free to flex and is thus exposed whensaid pressure is emanating from the opposite direction.

8. The improvement of claim 1 wherein said seat means and saidcircumferential sealing surface are in interference fit in relation toeach other in said closed position in the absence of the action ofinternal fluid pressure on said valve.

9. in a butterfly valve comprising annular flexible seat meanscircumscribing the fluid flow channel defined by the interior surfacesof a valve housmg, a disc mounted in said valve housing for rotationabout an axis substantially perpendicular to the flow axis of said fluidflow channel, and a circumferential sealing surface on said disccooperating with said seat means to block the flow of fluid through saidfluid flow channel when said disc is rotated into the closed position,said sealing surface being a segment of a substantially convergingsurface, the improvement comprising:

providing annular flexible seat means which tend to deflect more thanthe said disc in the downstream direction when internal fluid pressureof a given magnitude is applied from the direction of convergence ofsaid sealing surface and which also tend to deflect less than said discwhen said fluid pressure is applied from the opposite direction,

whereby internal fluid pressure, regardless of the direction from whichit is applied, increases the sealing effectiveness of said seat means onsaid disc wherein said annular flexible seat means comprise an annularouter element adapted to be constrained between adjacent surfaces of theelements constituting said valve, an inner element disposed within saidannulus of said outer element and containing an inclined seating surfaceadapted to seat against said convergent circumferential sealing surfaceon said disc, and a flexible linking element joining said inner elementto said outer element and permitting said inner element to deflect in adownstream direction in response to the application thereto of fluidpressure emanating from either direction along said fluid flow channel,and

wherein a rigid element adjacent to said inner element intercepts saidinner element as it tends to deflect in response to internal fluidpressure of a magnitude not greater than the design pressure of saidvalve and emanating from the direction opposite to said direction ofconvergence, and

wherein said rigid element is located in such proximity to said innerelement as to permit less deflection thereof in said direction ofconvergence than said inner element is free to deflect in the oppositedirection.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Pat nt 3 I DatedSeptember 28 1971 Inventor(5) David A. Helman et al It is certified thaterror appears in the above-identified patent and that said LettersPatent are hereby corrected as shown below:

Column 2 line 26 "a" should be the (second instance) column 2, line 56after "only" insert a celumn 2, line 63 "that seat" should be the seatQiolunm 3, line 3 "dripped" should be gripped Column 3, line 51 after"by" insert the Column 5, line 14 "not" should be now Column 6, line 59"an" should be and Column 7, line 15 "surface" should be surfaces Signedand sealed this 21st day of March 1972.

EnwARD M.FLETCHER, .m. ROBERT GOITSCHALK .J:lt1testing OfficerCommissioner of Patents 5 FORM po'wso uscomwoc 60376-P69 9 US GOVERNMENTPRINUNG OFFICE 1969 O365-334

1. In a butterfly valve comprising annular flexible seat meanscircumscribing the fluid flow channel defined by the interior surfacesof a valVe housing, a disc mounted in said valve housing for rotationabout an axis substantially perpendicular to the flow axis of said fluidflow channel, and a circumferential sealing surface on said disccooperating with said seat means to block the flow of fluid through saidfluid flow channel when said disc is rotated into the closed position,said sealing surface being a segment of a substantially convergingsurface, the improvement comprising: providing annular flexible seatmeans which tend to deflect more than the said disc in the downstreamdirection when internal fluid pressure of a given magnitude is appliedfrom the direction of convergence of said sealing surface and which alsotend to deflect less than said disc when said fluid pressure is appliedfrom the opposite direction, whereby internal fluid pressure, regardlessof the direction from which it is applied, increases the sealingeffectiveness of said seat means on said disc.
 2. The improvement ofclaim 1 wherein said annular flexible seat means comprise an annularouter element adapted to be constrained between adjacent surfaces of theelements constituting said valve, an inner element disposed within saidannulus of said outer element and containing an inclined seating surfaceadapted to seat against said convergent circumferential sealing surfaceon said disc, and a flexible linking element joining said inner elementto said outer element and permitting said inner element to deflect in adownstream direction in response to the application thereto of fluidpressure emanating from either direction along said fluid flow channel.3. In a butterfly valve comprising annular flexible seat meanscircumscribing the fluid flow channel defined by the interior surfacesof a valve housing, a disc mounted in said valve housing for rotationabout an axis substantially perpendicular to the flow axis of said fluidflow channel, and a circumferential sealing surface on said disccooperating with said seat means to block the flow of fluid through saidfluid flow channel when said disc is rotated into the closed position,said sealing surface being a segment of a substantially convergingsurface, the improvement comprising: providing annular flexible seatmeans which tend to deflect more than the said disc in the downstreamdirection when internal fluid pressure of a given magnitude is appliedfrom the direction of convergence of said sealing surface and which alsotend to deflect less than said disc when said fluid pressure is appliedfrom the opposite direction, whereby internal fluid pressure, regardlessof the direction from which it is applied, increases the sealingeffectiveness of said seat means on said disc, and wherein said annularflexible seat means comprise an annular outer element adapted to beconstrained between adjacent surfaces of the elements constituting saidvalve, an inner element disposed within said annulus of said outerelement and containing an inclined seating surface adapted to seatagainst said convergent circumferential sealing surface on said disc,and a flexible linking element joining said inner element to said outerelement and permitting said inner element to deflect in a downstreamdirection in response to the application thereto of fluid pressureemanating from either direction along said fluid flow channel, andwherein the deflection of said inner element occurs by virtue of flexurein said linking element about one of a pair of pivot points on saidadjacent surfaces, said pivot point on that side of said annular seatmeans facing said direction of convergence being located closer to thecenter of said annular seating means than said pivot point on the otherside thereof, whereby internal fluid pressure of a given magnitude tendsto deflect said inner element more when applied from the said directionof convergence than when applied from the opposite direction.
 4. Theimprovement of claim 2 wherein a rigid Element adjacent to said innerelement intercepts said inner element as it tends to deflect in responseto internal fluid pressure of a magnitude not greater than the designpressure of said valve and emanating from the direction opposite to saiddirection of convergence.
 5. The improvement of claim 1 wherein a rigidelement is located adjacent said flexible annular seat means and on thesame side thereof as the said direction of convergence, said rigidelement being positioned sufficiently close to said flexible annularseat means to intercept the deflection of said annular flexible seatmeans in response to internal fluid pressure of a magnitude not greaterthan the design pressure of said valve and emanating from the directionopposite to said direction of convergence.
 6. In a butterfly valvecomprising annular flexible seat means circumscribing the fluid flowchannel defined by the interior surfaces of a valve housing, a discmounted in said valve housing for rotation about an axis substantiallyperpendicular to the flow axis of said fluid flow channel, and acircumferential sealing surface on said disc cooperating with said seatmeans to block the flow of fluid through said fluid flow channel whensaid disc is rotated into the closed position, said sealing surfacebeing a segment of a substantially converging surface, the improvementcomprising: providing annular flexible seat means which tend to deflectmore than the said disc in the downstream direction when internal fluidpressure of a given magnitude is applied from the direction ofconvergence of said sealing surface and which also tend to deflect lessthan said disc when said fluid pressure is applied from the oppositedirection, whereby internal fluid pressure, regardless of the directionfrom which it is applied, increases the sealing effectiveness of saidseat means on said disc wherein a rigid element is located adjacent saidflexible annular seat means and on the same side thereof as the saiddirection of convergence, said rigid element being positionedsufficiently close to said flexible annular seat means to intercept thedeflection of said annular flexible seat means in response to internalfluid pressure of a magnitude not greater than the design pressure ofsaid valve and emanating from the direction opposite to said directionof convergence, and wherein said rigid element is located in suchproximity to said flexible annular seat means as to permit lessdeflection thereof in said direction of convergence than said flexibleannular seat means is free to deflect in the opposite direction.
 7. Theimprovement of claim 1 wherein the projection upon a plane perpendicularto the said flow axis of that portion of the surface of said flexibleseat means which is free to flex and is exposed to internal fluidpressure when said pressure is emanating from the direction ofconvergence contains a greater area than the projection upon the sameplane of that portion of the surface of said flexible seat means whichis free to flex and is thus exposed when said pressure is emanating fromthe opposite direction.
 8. The improvement of claim 1 wherein said seatmeans and said circumferential sealing surface are in interference fitin relation to each other in said closed position in the absence of theaction of internal fluid pressure on said valve.
 9. In a butterfly valvecomprising annular flexible seat means circumscribing the fluid flowchannel defined by the interior surfaces of a valve housing, a discmounted in said valve housing for rotation about an axis substantiallyperpendicular to the flow axis of said fluid flow channel, and acircumferential sealing surface on said disc cooperating with said seatmeans to block the flow of fluid through said fluid flow channel whensaid disc is rotated into the closed position, said sealing surfacebeing a segment of a substantially converging surface, the improvementcomprising: proViding annular flexible seat means which tend to deflectmore than the said disc in the downstream direction when internal fluidpressure of a given magnitude is applied from the direction ofconvergence of said sealing surface and which also tend to deflect lessthan said disc when said fluid pressure is applied from the oppositedirection, whereby internal fluid pressure, regardless of the directionfrom which it is applied, increases the sealing effectiveness of saidseat means on said disc wherein said annular flexible seat meanscomprise an annular outer element adapted to be constrained betweenadjacent surfaces of the elements constituting said valve, an innerelement disposed within said annulus of said outer element andcontaining an inclined seating surface adapted to seat against saidconvergent circumferential sealing surface on said disc, and a flexiblelinking element joining said inner element to said outer element andpermitting said inner element to deflect in a downstream direction inresponse to the application thereto of fluid pressure emanating fromeither direction along said fluid flow channel, and wherein a rigidelement adjacent to said inner element intercepts said inner element asit tends to deflect in response to internal fluid pressure of amagnitude not greater than the design pressure of said valve andemanating from the direction opposite to said direction of convergence,and wherein said rigid element is located in such proximity to saidinner element as to permit less deflection thereof in said direction ofconvergence than said inner element is free to deflect in the oppositedirection.